1. Field of the Invention
This invention relates to an image forming apparatus for use with copying machines, printers, plotters, facsimile apparatus and like apparatus.
2. Description of the Related Art
As one of conventional image forming apparatus, an image forming apparatus is disclosed in U.S. Pat. No. 3,689,935 wherein a voltage is applied to an electrode, which has a plurality of openings (hereinafter referred to as apertures) formed therein, in accordance with image data to control passage of toner particles through the apertures so that those toner particles passing through the apertures may form an image on a support member.
The image forming apparatus just described includes a flat plate made of an insulating material, a continuous reference electrode formed on one face of the flat plate, and a plurality of control electrodes formed on the other face of the plate member in an isolated relationship from each other. The image forming apparatus further includes an aperture electrode member extending, for each of the control electrodes, through the flat plate, the reference electrode and the control electrode and having at least a row of apertures formed therein, means for selectively applying a potential between the reference electrode and the control electrodes, means for supplying charged toner particles so that flows of toner particles to pass through the apertures may be modulated by the thus applied potential, and means for moving a support member and the aperture electrode member relative to each other to position the support member in the flow paths of the toner particles.
With this apparatus, however, the apertures are choked with toner particles to deteriorate the recording quality, and besides, the recording speed cannot be made very high.
The applicant of the present application has proceeded with further investigations and proposed an image recording apparatus disclosed in European Patent No. 587,366 (Japanese Patent Laid-Open Applications Nos. Hei 6-155798 and Hei 6-79907) wherein a carrying member which carries toner particle thereon and an aperture electrode member are disposed in a mutually contacting relationship with each other, thereby improving the recording characteristic remarkably. With the apparatus, since toner particle is supplied in contact with the aperture electrode member around apertures of the aperture electrode member, toner particle which causes choking of the apertures is not deposited in the apertures, and consequently, the apertures are not choked.
With the conventional image forming apparatus, however, when toner particles on the aperture electrode member and the toner carrying member slidably moves in contact with them, it is pressed against the aperture electrode member, and consequently, transportation of the toner particle is sometimes retarded on contacting faces of the aperture electrode member and the toner carrying member. When toner particle is contacted with the aperture electrode member, the contacting portion of the aperture electrode member is charged and toner particle is caused to stay there. If toner particle stays, then succeeding toner particle is not transported regularly to the downstream side of the thus staying toner particle in the direction of transportation of toner particle. Consequently, the toner particle transportation condition is rendered unstable and toner particle may not be supplied uniformly to the apertures. As a result, the problem that a large amount of toner particle is transported into one of the apertures while no toner particle is transported into another of the apertures at all arises, resulting in irregularity in an output image in the direction of the arrangement of the apertures, which makes the output image unattractive and of poor quality.